feat(mornye): add persistent accent color choices

lib/widgets/audio_analysis_spectrogram.dart

@@ -147,7 +147,10 @@ class _SpectrogramView extends StatelessWidget {
     // The plot stays black in both appearances; its controls need matching
     // contrast even when the surrounding Mornye page uses the light theme.
     return context.isMornye
-        ? Theme(data: MornyeTheme.build(Brightness.dark), child: card)
+        ? Theme(
+            data: MornyeTheme.fromContext(context, brightness: Brightness.dark),
+            child: card,
+          )
         : card;
   }
 

lib/widgets/mornye_artist_header.dart

@@ -40,7 +40,10 @@ class _MornyeArtistSurfaceState extends State<MornyeArtistSurface> {
 
   @override
   Widget build(BuildContext context) {
-    final darkTheme = MornyeTheme.build(Brightness.dark);
+    final darkTheme = MornyeTheme.fromContext(
+      context,
+      brightness: Brightness.dark,
+    );
     return Theme(
       data: darkTheme.copyWith(
         colorScheme: darkTheme.colorScheme.copyWith(primary: Colors.grey),

lib/widgets/mornye_context_menu.dart

@@ -172,7 +172,7 @@ class MornyeContextMenu extends StatelessWidget {
   Widget build(BuildContext context) {
     final theme = inheritSurface
         ? Theme.of(context)
-        : MornyeTheme.build(Theme.of(context).brightness);
+        : MornyeTheme.fromContext(context);
     final visibleGroups = groups.where((group) => group.isNotEmpty).toList();
     final shortcuts = quickActions.isEmpty
         ? null

lib/widgets/mornye_player_actions_sheet.dart

@@ -17,7 +17,7 @@ class MornyePlayerNavigationMenu extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final theme = MornyeTheme.build(Brightness.dark);
+    final theme = MornyeTheme.fromContext(context, brightness: Brightness.dark);
     final art = mediaItem.artUri;
     final source = art?.scheme == 'file' ? art!.toFilePath() : art?.toString();
     return Theme(